ABSTRACT
Life on Earth is almost totally dependent on the regular input of energy that is supplied by radiation from the Sun. The input maintains the temperature of most of the sea and the land surface within a range that allows living creatures to function. Some of the sunlight provides the energy for photosynthesis, the process plants use to convert carbon dioxide and water into oxygen and carbohydrates such as glucose. The products of photosynthesis contain more energy than the starting materials, and other life forms, such as animals and fungi, can exploit the stored energy. The animals inhale the oxygen and consume the plants, either directly (herbivores) or indirectly (carnivores), and return carbon dioxide and water to the environment.
